The present invention relates to a slide projector, and more specifically to a portable planetarium projector for use in the home.
As we move into the next Millennium, there is an increase in the already high interest in the scientific study of astronomy, and also in astrology. Many people visit exhibitions and shows which demonstrate, in simple terms, the movements of stars and other celestial bodies during an hour, day, month or year. Such demonstrations are usually held in large areas and in front of large audiences, due to the complexity and cost of the planetarium required in order to demonstrate the astronomy as accurately as possible.
A planetarium has, by dictionary definition, a projector that projects the positions and movements of stars and planets on to a hemispherical domed ceiling in order to simulate the night sky to an audience seated below. Although this definition stipulates a the presence of a hemispherical domed ceiling, a planetarium, for the purposes of this specification, should be interpreted to include a substantially planar display surface.
Hereto, all mechanical planetarium projectors use spherical or hemispherical surfaces on which a star field representation is held before being projected onto a dome shaped surface. A computer-based planetarium projector is known, which has a star field projected from a flat computer screen, as described for example in UK Patent No. 2,050,775. The software is, however, written for the projection of the star field image onto a domed surface.
The problem with all current planetarium projectors is that purpose-built domed auditoria must be built in order to accurately display the night sky, with the all the celestial bodies in their correct orientations and positions.
Temporary domed structures, such as large inflatable domes, of about 3.5 to 4.5 meters diameter, can be filled with air to demonstrate astronomy, although experts are required to run the demonstration, and the costs can be as large as £10,000. Such planetariums are more suitable for hiring by schools to demonstrate simple astronomy to their pupils.
A children""s toy is currently available that comprises a bulb within a transparent ball that may provide some sort of night sky display, when projected on to an outside surface. This is very much limited to being a toy, however, and does not provide an accurate projection for the purposes of studying astronomy.
A conventional planetarium projector comprises a spherical body located around a central light source. The spherical body has an array of pinholes in its surface, through which light is projected from the internal light source. The pinholes do not have any lens assembly. This leads to a projection of dim and fuzzy star, and celestial body, representations.
Furthermore, conventional planetarium projectors require a great deal of skill and training to be operated effectively.
There are currently no accurate planetarium projectors available that are suitable for use by an individual in the home, due to the size, complexity and cost of planetarium projectors, and the requirement for a large domed surface on which to project the star field.
The present invention seeks to alleviate the aforementioned disadvantages by. providing a slide projector that is portable, easy to use, of reasonable cost, and is suitable for use by an individual, or individuals, in the home. In particular, the present invention eliminates the necessity for a domed surface on which to project the night sky in the case of planetarium projector.
Accordingly, there is provided, a slide projector comprising projection means for directly projecting an image from a slide perpendicularly onto a projection surface, the projection means being such that the projected image of the slide lies, in use, in a substantially planar projection surface, the projection means comprising a light source and at least two vertically juxtaposed slides, parallel to each other.
Preferably, images are projected vertically from the slide onto a substantially planar projection surface and the slides are in the horizontal plane.
In a preferred embodiment, the slide projector comprises two vertically-juxtaposed slides, parallel to one another in the horizontal plane.
Preferably, one of the slides is rotatable while the other slide remains in a fixed position. Alternatively, both slides may be rotatable or both slides may remain in fixed positions.
The slide projector may also have means for retaining the slides in a set position, preferably by providing an air flow above and below the slides. Preferably, the slides are retained due to a sub-atmospheric pressure that is formed below the slides.
Preferably, the slide will display images of astronomy such as starfields and other celestial bodies
Preferably still, the fixed slide is one that, in use, displays an image of the sky""s horizon. The rotatable slide is preferably one that, in use, displays the image of night sky showing a starfield and/or various other celestial bodies.